# GHSA-w44r-93j7-qv28: The client records the server-selected key-exchange group per server name when it processes the ServerHello, before the server is authenticated. - **Severity:** Not scored - **Exploited in the wild:** Not known - **Fix available:** Yes - **Published:** 14 Oct 2026 - **Also known as:** RUSTSEC-2026-0349 ## What is GHSA-w44r-93j7-qv28? GHSA-w44r-93j7-qv28 is a vulnerability in rustls, published on 14 Oct 2026. ### Official description ## Summary The client records the server-selected key-exchange group per server name when it processes the ServerHello, before the server is authenticated. A network attacker can answer one connection attempt for a target name with a ServerHello that selects X25519 and close the connection. Later ClientHellos for that name carry one X25519 share while supported_groups still lists X25519MLKEM768 first. If the server accepts that share instead of sending a HelloRetryRequest, the handshake completes with classical key exchange only and no error. An attacker that answers one connection attempt for the target name with a ServerHello selecting X25519 changes every later ClientHello of that client for that name, for as long as the entry stays in the store. No certificate or completed handshake is needed: it parses the ClientHello, sends the ServerHello, and closes. TLS 1.3 transcript binding stops an on-path attacker from editing the ClientHello of one connection. It does not stop the attacker from steering the client's prediction state beforehand, because that state is written from an unauthenticated message. ## What does not trigger it - Servers that send a HelloRetryRequest. The connection stays hybrid and costs one extra round trip. - A client configuration with resumption disabled: nothing is stored. - A different server name: the record is per name. ## Impact If the genuine server picks the group for which a share is present, instead of sending a HelloRetryRequest for its preferred hybrid group, the handshake completes with classical key exchange only, between two peers that both support the hybrid group. No error is raised. The confidentiality of recorded sessions against a future quantum adversary is lost for those connections (harvest now, decrypt later). There is no key compromise and no authentication bypass. Note that this behaviour is discussed at length in [draft-ietf-tls-key-share-prediction](https://www.ietf.org/archive/id/draft-ietf-tls-key-share-prediction-01.html#name-security-considerations) so the actual security impact is largely down to a server policy decision. ## Which versions are affected by GHSA-w44r-93j7-qv28? 5 open source packages ship an affected version, including rustls. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `rustls` | crates.io | All versions | 0.23.46 | | `rustls` | crates.io | All versions | 0.23.46 | | `rustls` | crates.io | From 0.0.0-0 | 0.23.46 | | `rustls` | crates.io | From 0.24.0-dev.1 | 0.24.0-dev.2 | | `rustls` | crates.io | From 0.24.0-dev.1 | 0.24.0-dev.2 | ## How do I fix GHSA-w44r-93j7-qv28? Upgrade rustls to a fixed version for your release line: 0.23.46 or 0.24.0-dev.2. ## Is GHSA-w44r-93j7-qv28 being exploited? There is no known exploitation of GHSA-w44r-93j7-qv28 in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for GHSA-w44r-93j7-qv28 and fix it if it is affected. What it is: GHSA-w44r-93j7-qv28 is a vulnerability in rustls, published on 14 Oct 2026. Exploitation: There is no known exploitation of GHSA-w44r-93j7-qv28 in the wild and no public exploit code. Affected packages and fixed versions: - rustls (crates.io): affected all versions; fixed in 0.23.46 - rustls (crates.io): affected all versions; fixed in 0.23.46 - rustls (crates.io): affected from 0.0.0-0; fixed in 0.23.46 - rustls (crates.io): affected from 0.24.0-dev.1; fixed in 0.24.0-dev.2 - rustls (crates.io): affected from 0.24.0-dev.1; fixed in 0.24.0-dev.2 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/GHSA-w44r-93j7-qv28/ (Markdown: https://insights.sbomify.com/GHSA-w44r-93j7-qv28/index.md) ``` ## Sources - OSV: https://osv.dev/vulnerability/GHSA-w44r-93j7-qv28 --- From sbomify Insights: https://insights.sbomify.com/GHSA-w44r-93j7-qv28/ Summaries are generated and may contain mistakes; the official description above is the record.